The performance improvement of TPO (thermoplastic polyolefin) composite steel sheet is mainly due to the complementary advantages of each layer of materials in its multi-layer structure. The steel sheet provides high strength and good mechanical properties, while the TPO layer increases corrosion resistance, chemical resistance and good weather resistance. In addition, the flexibility and impact resistance of TPO can improve the overall durability and service life of the steel sheet. This composite structure combines the rigidity of steel with the protective properties of TPO, making the composite steel sheet perform better in roof waterproofing applications.